Normally a brake block holder, which may be suspended from a bracket on the brake actuator, moves along an arc with a big radius but otherwise in line with the push rod. In such a case the force transmission can be accomplished by simple means, for example by an edge and recess arrangement as shown in GB-B-1 140 488, allowing the necessary sliding relative movement.
If the brake block holder is also laterally movable in relation to the push rod, which is the case in certain recent designs allowing the brake block holder to follow axial movements of a wheel or wheel-set, the force transmission problem has to be solved in other ways. One typical example of such a solution is shown in U.S. Pat. No. 4,287,968, where there is a separate force transmission member with certain properties between the push rod and the brake block holder. This publication is taken as the closest prior art.
Although this latter prior art solution has great advantages and has proven commercially successful, it does not give perfect force transmission without transverse force components at the arcuate movements of the brake block holder.